Therapeutics is focused on the development of adjuvant systems with desired immune activities for targeted indications. The Company's immune stimulatory adjuvant platform builds on combinatorial use of immune agonists with distinct immune targets and mechanisms of action for the generation of therapeutic immune responses. Critical to this platform technology is the use of novel forms of tumor necrosis factor ligand (TNFL) costimulatory family agents that directly modulate innate, adaptive, and regulatory immunity and cross- talk with pattern recognition receptors for sustained immune effector responses. The Company's lead adjuvant system, ISAS-01, constitutes a novel form of 4-1BBL/streptavidin chimeric molecule formulated with monophosphoryl lipid A (MPL) as an agonist of toll-like receptor 4 (TLR4). The choice of 4-1BBL is based on the pleiotropic effects of 4-1BB costimulatory signaling in cells of innate (NK cells, NKT cells, macrophages, neutrophils, and DCs), adaptive (CD4+ and CD8+ T cells), and regulatory (CD4+CD25+FoxP3+ T regulatory (Treg) cells) immunity, and the critical role of coordinated responses of these cell populations in the eradication of cancer and control of recurrences. MPL complements the immune activities of 4-1BBL by upregulating the 4-1BB receptor and ligand on antigen presenting cells, and 4-1BBL physically interacts with TLRs for sustained innate immune responses. Therefore, the combined use of these two agents has the potential to generate robust immune effector responses and overcome immune evasion mechanisms, culminating in the eradication of cancer and control of recurrences. In support of this, we have recently shown that ISAS-01 as the adjuvant component of TAA-based protein vaccines was effective in eradicating tumors in various preclinical models. A mucin 1 (MUC1) TAA-based vaccine, tecemotide, against non-small cell lung cancer being developed by Merck KGaA has failed to meet its primary endpoint of improving overall patient survival in a phase III clinical study. Factors contributing to the vaccie inefficacy are unknown. We hypothesize that the lack of a potent adjuvant system able to generate a robust immune effector response as part of vaccine formulation, as well as the need to overcome tumor immune evasion mechanisms may have contributed to the vaccine failure. Therefore, the main objective of this Phase I STTR application is to test if the ISAS-01 adjuvant system generates robust cellular immune responses against MUC1 TAA and improves therapeutic efficacy of the tecemotide-based vaccine formulation using MUC1 transgenic (TG) mice as a stringent preclinical tumor model. Three specific Aims are designed to i) establish a reformulated vaccine that generate robust Th1 responses to MUC1 TAA, ii) assess the therapeutic efficacy of the vaccine in eradicating lung carcinoma in MUC1 TG mice, and iii) investigate immune responses associated with vaccine efficacy/failure. A better efficacy for the reformulated vaccine over the tecemotide-based vaccine formulation will indicate the need for further development of this vaccine and potential for entry into phase I clinical trials for lung cancer.